Automatic testing system



1,612,767 0. E. LOMAX l AUTOMATIC TESTING SYSTEM Dec. -28 1926.

2 Sheets-Sheet 1 Filed Sept. 1921 4 f p i 1 v 1 -Im ren ELF- Elsi-JennaE.LEJTU.EX

Dec. 28 ,-1926. 1,612,767

0.15. LOMAX 7 AUTOMATIC TESTING SYSTEM Filed Se t/6, 1921 2 Sheets-Sheet2 mechanically of the same type as the switches D, F, and H and may havecircuits substantially the same as are shown in the United StatesLetters Patent #1332,- 217, granted March 2, 1920, to Jacobsen. Theconnector selectors referred to may be mechanically the same as theselector repeaters and may have circuits substantially the same as areshown in the United States Letters Patent #1,1G4:,4:79, granted Decemberat, 1915, to Deakin.

The line switches C and C are identical and are of the well known rotarytype in which the wipers have no normal position and move in a forwarddirection only.

Reference will now be had to United States Letters Patent No. 1,481,586,granted January 22, 1924, to Benson, which contains a completedisclosure of the necessary equipment for testing the subscribers linesthat terminate in the main exchange. The switches disclosed herein aredesigned to cooperate with the wire chiefs test circuits such as aredisclosed in the patent referred to and accordingly the trunk lineextending to the test distributor repeater F shown in the presentdrawings is assumed to terminate at the wire chiefs desk insubstantially the same manner as the trunk line extending to the testdistributor D in the Benson patent referred to.

The system, having thus been described generally, will now be describedin connection with a detailed description of the operation of theapparatus shown. For this purpose it will be assumed that the wire chiefin the main exchange desires to test the trunk line X.

In order to initiate a test connection the wire chief places a closedloop including the impulse springs of a calling device across theconductors 3 and 4 of the test distributor repeater F. In response tothe closure of this bridge line relays 9 and 7 energize and the latter,upon energizing, closes a circuit for repeating relay 12 at armature 28,whereupon the said relay energizes. As a further result of theenergization of line relay 7 it closes a circuit for release relay 8 atarmature 27. Upon energizing, release relay 8 opens a point in therelease magnet circuit at armature 30, at the same time preparing acircuit for the vertical magnet 16, and at armature 29 places ground onrelease trunk conductor 23. As soon as ground is placed on release trunkconductor 23 a circuit is closed for the lower or polarizing winding 0 fel-ectropolarized relay 13 but this winding alone, consisting of fewturns of high resistance, is not able to effectively energize the relay.

The wire chief now operates his calling device in accordance with thefirst digitof the desired number, thereby interrupting the circuit ofline relay 7 a corresponding number of times. Each time. line relay 7deenergizes in response to one of these interruptions it opens thecircuit of repeating relay 12 at armature 28. Repeating relay 12,therefore, falls back each time line relay 7 does but does not performany function at this time. as a further result of each deenergization ofline relay 7 it closes at armature 27 the following circuit: fromground, by way of armature 27 and its resting contact, armature 30 andits working contact, the contact of off normal spring 22 and saidspring, series relay 10, and vertical magnet 16 to battery. By theoperation of the vertical magnet the switch shaft and wipers are raisedstep by step until the latter come to rest opposite the level ofcontacts in which the desired trunk line terminates. Relay 10 isenergized in series with the vertical magnet 16 and being slow actingretains its armature attracted throughout the Verti- (Al movement,thereby maintaining the circuit of vertical magnet 10 in act after theoff normal springs have shifted as they do upon the first vertical step.

At the end of the vertical movement slow acting series relay 10 fallsback and at armature 32 shifts the circuit from the vertical to therotary magnet.

The wire chief now manipulates his calling device in accordance with thesecond digit of the desired number, whereupon line relay 7 isdeenergized a corresponding number of times and, upon eachdeenergization, completes the following circuit: from ground by way ofarmature 27 and its resting contact, armature 30 and its workingcontact, normally open contacts controlled by off normal spring 22,armature 32 and its resting contact, armature 43 and its restingcontact, and rotary magnet 17 to battery. By the operation of the rotarymagnet the shaft and wipers of the switch F are rotated step by stepuntil the latter come to rest upon the desired set of contacts which weshall assume in this case are the contacts 6165, inclusive. Slow actingrelay 11 is maintained energized in multiple with the rotary magnet 17throughout the series of interruptions and at armature 83 maintains thetest wiper 52 disconnected. At the end of the rotary movement slowacting relay 11 deenergizes and connects up the test wiper 52 atarmature 33, thereby completing the following circuit: from ground, byway of release trunk conductor 23, upper winding of switching relay let,armature 38 and its resting contact, resting contact of armature 39 andsaid armature, test wiper 52, test contact 6?), conductor 66, and relay101 to battery. Relays 1 1 and 101 energize over the above tracedcircuit and the latter connects up the private normal conductors of allthe trunk lines belonging to the branch exchange in which the trunk linecomprising conductors 67-70 inclusive, terminates, at armatures 104-,105, and at other armatures which may be provided but which are notshown.

In the switch F, switching relay 14, upon energizing, closes a lockingcircuit for it self at armature 12; opens the circuit of the rotarymagnet 17 at armature 13; places direct. ground on test wiper 52 atarmature 39; extends the heavy test. conductors 2 and 5 at arniiatures38 and a4; closes a circuit for the control relay 75 of the trunkbusying switch D at armature 41; and at armature 40 places the followingbridge across trunk conductors 68 and 69: from conductor 69 by way ofbank contact 6%, wiper 53, armature 36 and its working contact, upperwinding of electropolarized relay l3, armature 10 and its workingcontact, wiper 51, and bank contact 62 to conductor 68. Current beginsto flow through the upper winding of electrcpolarized relay 13 as soonas this bridge is closed but the said relay in not energized at this tme "for the reason that the current flowing through the upper winding isopposite in direction to that flowing through the lower winding.

In the branch exchange, line relays 151 and 153 of the test connector Henergize in response to the placing of the above traced bridge acrossthetrunk conductors 68 and 69. Line relay 151, upon energizing, closes acircuit for release relay 152 and the latter, upon energizing, preparesa' circuit for vertical magnet 166 at armature 163.

Returning now to the trunk busying switch D in the. main exchange, wefind that control relay 75,- upon energizing, in re sponse to theclosure of its circuitat armature 11 of switching relay ll, closescircuit for release relay 76 at armature 86. Release relay 76, uponenergizing, prepares a circuit for vertical magnet 80 at armature 88. v

The condition that now exists is that the testdistributor repeater F hasbeen operated to connect with a test connector located in the branchexchange inwhich the trunk line that the wire chief desires to testterminates, and the said test connector is ready for operation. Further,the trunk busying switch D in the main exchange is ready to be operatedin response to the next digit called.

As it is the usual practice to have all the trunk lines from the main tothe branch exchange terminate inthe tenth level of the switches at thebranch exchange, we shall assume that such is the case in the presentsystem. Accordingly the wire chief manipulates his calling device inaccordance with the digit 0, whereupon line relay 7 of switch I isale-energized ten times momentarily and upon each deenergization closesthe circuit of slow acting relay llat armature 27 and at armature 28opens the circuit of repeatcompletes ing relay 12. Each timerepeating'relay 12 deenergizes it opens the bridge across trunkconductors 68 and 69 at armature 36, and at armature opens the circuitof control relay 7 5 of the trunk busying switch D. Each time controlrelay 7 5 deenergizes it closes at armature 86 the following circuit:from ground by way of armature 86 and its resting contact, armature 88and its working contact, the contact of off normal sprng 9i and saidspring, relay 77,'and vertical mag net to battery. By the operation ofthe vertical magnet the shaft and wiper of the switch I) are raised stepby step until the latter stands opposite the tenth level of bankcontacts. Relay 77 is energized in series with vertical magnet 80 andbeing slow acting retains its armature attracted throughout the verticalmovement, thereby maintaining the circuit of the vertical magnet intactafter the off normal springs have shifted as they do upon the firstvertical Step. At the end of the vertical movement slow acting relay 77deenergizes and transfers the operating circuit from the veitFcal to therotary magnet.

In the branch exchange, line relay 151 of the connector H is deenergizedten times momentarily in response to the interruptions produced in itscircuit, at armature 86 of repeating relay 12 of test distributorrepeater F, and, upon each deenerglzation, the following circuit: fromground and by way of armature 159 and its resting contact, armature 163and its working contact, the contact of oil normal spring 171. and saidspring, relay lo l, andvertical magnet 166 to battery. By the operationof the vertical magnet the shaftand wipers of the test connector H areraised step by step until the latter stand opposite the desired level ofbank contacts which in this case is the tenth. Relay 154- is energizedin series with the vertical magnet and being slow acting retains itsarmature attracted through the vertical i'i'iovement, therebymaintaining the circuit of the vert cal magnet intact after the oilnormal springs have shifted as they do upon the first vertical step. Atthe end of the vertical movement 1 4 slow acting relay 15 1 deenergizesand at armature 167 transfers the circuit from the vertical to therotary magnet.

In the main exchange the trunk busying 1 switch D has its wiper steppedup opposite to the tenth level of bank contacts and in the branchexchange the test connector H has its wipers 177-179, inclusive, steppedup opposite the tenth level of bank contacts.

I'Vith this condition existing, the wire chief manipulates his callingdevice in accordance with the digit 1, which is the digit .ed to thetrunk line X which he (lesires to test, whereupon control relay 75 ofthe trunk busying switch D and line relay 151 of the test connector Hwill both be deenergized one time momentarily. Upon deenergizing, thecontrol relay of switch D operates the slow acting series relay 78 andthe rotary magnet 81 in series. Rotary magnet 81, upon energizing,advances the switch wiper 95 into engagement with bank contact 96. Slowacting relay 78, upon energizing, disconnects the test wiper 95 atarmature and closes a circuit for slow acting relay 79 at armature 91.

At the end of the rotary movement slow acting series relay 78 fallsback, connects up the test wiper at armature 90, and at amiature 91opens the initial circuit of slow acting relay 79. This relay in anyevent, however, being slow acting retains its armature attracted for aninterval In the branch exchange, line relay 151 of the test connector H,upon dcenergizing, operates the slow acting series relay 155 and rotarymagnet 175 in series. Rotary magnet 175, upon energizing, advances thewipers 177-179, inclusive, into engagement with the bank contacts180-182, inclusive, to which the trunk line X is multipled. Relay 155,upon energizing, disconnects the wipers 177 and 179 at armatures 172and176; disconnects the testwiper 178 at armature 168; and at armature 169opens a point in the circuit of reversing relay 150, at the same timeclosing the circuit of slow acting relay 156. At the end of the rotarymovement slow acting relay 155 deenergizes, connects up the wipers 177and 179 at armatures 172 and 176; connects up the test wiper at armature168; and at armature 169 opens the circuit of slow acting relay 156 andcloses the circuit of reversing relay 150.

From this point the operation depends upon whether the trunk line X isbusy or idle. If it is busy there is a ground potential on the releasetrunk conductor 183 in the branch exchange and upon release trunkconductor 113 in the main exchange and consequently on the test contact96 in the bank of the trunk busying switch D. Such being the case slowacting relay 79 of the switch D does not deenergize when its initialcircuit is opened at armature 91 by the falling back of slow actingrelay 7 8 but is main: tained energized from ground by way of releasetrunk conductor 113, armature and its working contact, conductor 98,bank contact 96, wiper 95, resting contact of armature 90 and saidarn'iature, armature 92 and its working contact, and relay 79 tobattery.

In the branch exchange slow acting relay 156 does not deonergize whenits initial circuit is opened at armature 169 of relay 155 but ismaintained energized over the follow ing circuit: from ground, by way ofrelease trunk conductor 183, test contact 181,

test wiper 178, armature 164 and its working contact, resting contact ofarmature 168 and said armature, armature 17 1 and its working contact,and relay 156 to, battery. According to the usual practice the callingwire chief is given reversed battery supervision at this time so as toinform him of the busy condition of the called trunk line. It will beremembered that slow acting relay 155, upon deenergizing, closed thecircuit of reversing relay 150 at armature 169 in series with theworking contact of armature 173 and the said armature. Upon energizing,reversing relay 150 reverses the incoming trunk conductors 68 and 69,thereby causing a reversal of current flow in the bridge across theseconductors including the upper winding of electropolarized relay 13 ofthe test distributor repeater F, The two windings of electropolarizedrelay 13 which heretofore have opposed each other now assist each otherin operating the said relay. Upon operating, relay 18 closes at armature87 the circuit of reversing relay 6 and the said relay, upon energizlng,reverses the trunk conductors 3 and 1 with the final result that thebusy lamp is lighted before the calling wire chief to inform him of thebusy condition of the called line.

The heavy test conductors are now connected with the talking conductorsof the trunk line X and the wire chief may associate his head settherewith so as to find out if the trunk line X is actually in use or ifit tests busy on account of being out of order. In case the wire chiefupon listening in learns that the called trunk line is not in use, hemay disassociate his head set from the heavy test conductors and makeany desired tests.

Assuming now that the wire chief discovers that the trunk line X is inuse he has two courses to follow. He may release the connection and callagain later or he may hold up the connection until the trunk line Xbecomes idle. Assuming that he does the latter, slow acting relay 79 ofthe trunk busying switch D deenergizes, upon the removal of the groundpotential from release trunk conductor 113 of the trunk line X in themain exchange, which occurs as soon as the trunk line becomes idle. Assoon as relay 79 deenergizes, it replaces the ground potential onrelease trunk conductor 113 by way of the following path: from ground,by way of the working contact of armature 87 and said armature, restingcontact of armature 92 and the said armature, and thence by way of apreviously traced circuit to release trunk conductor 113. As soon asthis ground potential is replaced switching relay 11 1 of line switch Cenergizes in series with stepping magnet but the said stepping magnet isnot energized on account of the high resistance of switching relay 114..Relay 1141, upon energizing, disconnects the upper and lower conductorsof the trunk line X from the winding of line relay 116 and from groundat arniatures 117 and 118, respectively, but owing to a mechanicalinterlocking device (not shown) between the armature of said relay andthe armature of line relay 116, the armature of switching relay 114 isnot completely operated at this time and consequently therswitch wipers119121, inclusive, are not connected up.

In the branch exchange slow acting relay 156 upon deenergizing inresponse to the removal of the ground potential from release trunkconductor 183, opens'the circuit of reversing relay 150 at armature 173,and at armature 174 replaces the ground potential on release trunkconductor 183, whereupon switching relay 18% in the line switch C pullspart way up and removes battery and ground from the upper and lowerconductors of the trunk line X, respectively. Reversing relay 150, upondeenergizing in response to the opening of its circuit at armature 173of relay 156, reverses trunk conductors 6S and 69 back to normalwhereupon electropolarized relay 13 of the test distributor repeater Fretracts its armature, thereby opening the circuit of reversing relay 6which reverses the trunk conductors 3 and 4 bacl to normal. The visualbusy signal in front of the wire chief is now eXtin guished.

The wire chie'r may now make whatever tests he deems necessary on thetrunk line X, but since the present invention is not particularlyconcernedwith them they will not be described here.

In case the wire chief finds that the trunk line X tests 0. K. he maydecide to test the line switch C also to determine whether or not thesaid line switch is working properly and to ascertain whether or not heis able to call in to the main exchange from the branch exchange by wayof the trunk line X. lVit-h the assumption as above noted, the wirechief may perform certain operations with the result that direct; groundis placed on trunk conductor t of the test distributor repeator F andthe trunk conductor 3 is left open.

FvVith this condition existinv .2 relay 7 is maintained energized butline re- ;lay 9 deenergizesand at armature 81 places ground on trunkconductor 68 of connector -.hy" way of armatures 3 t and thereby short,circuiting line relay 153 of the test connector H. Upon deenergizing,line relay I53 removes ground from release trunk conductor 1.83 atarmature 164k, whereupon switching relay 184C of the line switch C.deenergizes and connects up line relay 185 ,to the {upper conductor ofthe trunk line X a tarmature 186, and at armature 187 places .ground onthe lower conductor of the said relay upon energizing, cioses thecircuit of tie stepping magnet and switliing relay in series andconnects up the test wiper 189 to a point between the two. The lineswitch C now operates in the weil known manner to s l an idle trunk lineextending to a c -nn ttor selector. [is soon as an idle trunk is toundswitching relay 184; energizes and extends the connection through to thebet-ore mentioned connector selector, where ugonthe line and releaserelays energize and the latter prepares the switch for operation andcloses a holding circuit for line switch C in the usual manner. Afterthe operations have proceeded thus far the wire chief may connect thetrunk conductors 3 and e of the tesa distributor repeater F together agein and remove the ground potential from the latter. hen this is doneline relay 5) ener 1268 and t armature 31 removes ground froin'trunl;conductor-68 oi the test connec tor H; Line relay 153 of the testconnector it now energizes and places a' multiple ground on the releasetrunk conductor 183 at armature 164.

T he wire chief may now operate his calldevice and extend the connectionthrough the regular trunking system from the bran-ch exchange to themain exchange and thence through the main exchange switches to atelephone located at his desk and in this manner determine whether ornot he is able to call in tothe branch exchange overthe trunk line X andout again.

lVc seall assume now that after having tested the trunk line X the wirechief decides to test another trunk line between the main and the samebranch exchange Since the trunk line X terminates in the first set ofcontacts in the bank of the test connector H he may operate his callingdevice .in accordance with the proper digit and cause the wipers 0t thesaid test connector to be stepped around into engagement with thedesired setof contacts. At the same time that the test connector H isbeing stepped around the trunk busying switch D in the main exchange isoperated to connect with the release trunk conductor of the called trunkline so as to make the called trunk line busy and remove the normalbattery and ground connections in the line switchin the ijnain exchangeThe test for busy at the end of the rotary movement is the same in thiscase as it was when the connection was epitended to the ,trunk line andaccordingly'need not be described.

As before pointed out the test connector I H in the first nine levelshas access to subscribers lines that terminate in the branch exchangeand the wire chief may test one of these lines in the same manner as hetests a trunk line such as trunk line X, after having called the properdigits so as to bring the wipers of the connector H into engagement withthe desired set of contacts. Now it will happen many times that a wirechief will wish to test a line which terminates in another level,immediately after having tested a line or a trunk line that terminatesin one level. \Vhen this occurs it is not necessary for the entireconnection to be released but the wire chief may release only the trunkbusying switch D and the test connector H. In order to do this the wirechief places battery on the trunk conductor 3 leading to the testdistributor repeater F and opens the trunk conductor 4. lVith thiscondition existing line relay 9 is maintained energized and line relay 7is deenergized. Upon deenergizing, line relay 7 opens the circuit ofrepeating relay 12 atarmature 28, the circuit of release relay 8,however, being closed through the working contact of armature 29 and thesaid armature, and armature 31 and its working-contact. Repeating relay12, upon (leenergizing, opens the circuit of control relay T5 of thetrunk busying switch D at armature S5 and at armature 36 opens thebridge across trunk conductors 68 and 69 whereupon line relays 151 and165 of the test connector H deenergize. The trunk busying switch D andthe test onnector H are now restored to normal position in a manner tobe explained more fully hereinafter. lVith the trunk busying switch Dand the test connector thus restored to normal position, the wire chiefmay restore the loop across trunk conductors 3 and 1, disconnect batteryfrom the latter, and operate his calling device in accordance with theproper digits, and thereby cause the said switches to connect with thedesired set of bank contacts.

It may be said at this time that the first nine levels of bank rent-actsin the trunk busying switch I may ordinarily be omitted the main tobranch exchange trunk lines seldom. tern'iinated in any level other etenth. It may be pointed out also time that the reason for making theline relay 9 of the test distributor repeater F slow to tleenergize isto prevent it from falling back and placing ground on trunk conductor 68at the beginning of a series of lllll'ltllHQS after the connection hasbeen extended to a test connector, such as test connector H. The slowacting line relay 9 however, may fall back before the series of impulsesis finished but prior to this time slow acting relay 11, which, isenergized throughout the series of interruptions has energized anddisconnected the resting contact of armature 31. In the event that linerelay 9 does deenergize during the series of interruptions it isenergized again at the end of the series before slow acting relay 11 hashad time to deenergize.

After having finished making the desired tests the wire chief removesthe bridge from across the trunk conductors 3 and 4 of the testdistributor repeater F, whereupon line relays 7 and 9 deenergize. Linerelay 7, upon deener -izing, opens the circuit of repeating relay 12 atarmature 28 and the said relay 12, upon deenergizing, opens the circuitof control relay 75 of the 'trunk busying switch D at armature and atarmature 36 opens the bridge across conductors (3S and 69 of the trunkline extending to the test connector H.

In the test connector H line relays 151 and 153 now deenergize and thelatter removes the ground potential from test wiper 178 at armature 164,whereupon the branch exchange end of the trunk line X tests busy nolonger. Line relay 151, upon deenergizing, opens the circuit of releaserelay 152 and completes the circuit of rotary magnet 17?) and the wipersare stepped around to the next contact set. Release relay 152,

upon deenergizing, opens the circuit of the rotary magnet and completesthe following circuit for release magnet 165: from ground by way ofarmature 159 and its resting contact, armature 163 and its restingcontact, reicasc link spring 160 and its working contact, and releasemagnet 165 to battery. Release magnet 165, upon energizing, forces thedouble dog 162 out of engagement with the shaft of the switch (notshown) whereupon the release link 161 moves downward over the end of thedouble dog in the manner shown, thereby retaining the said dog in place.As soon as the release link 161 moves downward, the circuit of therelease magnet 165 is opened and the following circuit is closed: fromground by way of release link spring 160 and its resting contact, offnormal contacts 170, and slow acting relay 197 to battery. The switchshaft which is released. as soon as the double dog 16: 5 is forced outof engagement with it, new returns to normal position and opens thecircuit of slow acting relay 197 at oil normal contacts 170. Relay 19?is made slightly slow acting so as to insure that its armature makes afull stroke in all cases. This is necessary as the off normal springsare opened very shortly after the release link spring 160 closes thecircuit of slow acting relay 197 by coming into e-ngagen'lent with itsown resting contact. It is seen that in any event the circuit of slowacting relay 19"- is closed only momentarily when the switch isfunctioning properly. Upon energizing, relay 197 closes at armature 196Lil a circuit for the meter M and the slow set- PEIL: in multiple. Themagnet of the meter ill now becomes energized and the number wheels areadvanced to register the call and the slow set SS begins to operate toforce the spring 198 into engagement with its working contact but doesnot hare time to do so in case the switch H is releasing properly.llelay 197, upon deenergizing, opens the circuitof meter M and the slowset at ar iature 196 whereupon the n agnet of t e meter M becomesdeenergized and the associated pawl is caused to engage another notch onthe number wheel, and the solenoid ot' the slow set SS, upondeenergizing, allows the dash pot arrangement to restore to normalposition immediately.

The function of the meterM is to register the number oi both completedand attempted calls, and it will obviously do so since it operates eachtime that any switch in the branch exchange is released, it beingunderstood oi coursethat the conductor eX- tending to slow acting relay197 is common to the test connector H and the regular connectorselectors in the branch exchange.

In case the test connector H becomes mechaniczlly stuck and does notrelease immediately the circuit of slow acting relay 197 is maintainedclosed for a. longer period of time than is usual and the circuit of thesolenoid of the slow set SS is consequently maintained closed longenough to allow the dash pot arrangement to be operated to force thespring 198 into engagement with its associated Contact, thereby closinga circuit tor the buzzer 199 so as to notify an attendant. It will benoted, however, that the circuit of the release magnet 165 is openedjust as soon as the release link 161 has dropped over the end of thedouble dog 162 and consequently the said release magnet, which isgenerally low wound so as to give it the necessary power, does not burnout or become hot, as has heretofore been the case, when the switchshaft remains stuck.

To continue with the description of the release of the connection, thetest connector l in the branch exchange is now restored onormalposition, the guarding ground Jotential is removed from releaseconductor the trunk line and the completed en registered on the meter M.In antime the switches D and F in the 'Xchange have been restored tonormal ll be explained now. Line 7 of the test distributor repeater lupon deenergizing, not only opens the cirof repeating relay 12 asexplained, but o opens the circuit of release relay 8 and acting relayll. Slow acting relay 11 becomes energized but does not have anyparicular t'unction at this time. Release relay ses the previouslytraced. circuit for slow upon deenergizing, opens the circuit of slowacti relay ll, closes a circuit for release magnet 15 by way of armature27 and its resting contact, armature and its resting contact, andrelease linl: saring 20 and its working contact. Upon energizing, re n'agnet l5 forces the double dog 18 out of engagement with the switchshaft, whereupon release link 19 drops over the end of said double dog18 thereby retaining the said dog place. The release link spring 20 mores downward at this time and opens the circuit or release magnet 15 andextends the circuit to the off normal spring 21 and its associatedcontact. he conductor extending from the contact associate-dv with theoil normal spring 21 is assumed to extend to a slow relay such as theslow relay 19?, Fig. with which there is associated. the same type ofequipment as associated with the slow acting relay 197. The shaft andwipers of the test distributor repeater F are now restored to normalposition, the circuit of the associated slow acting relay being openedat off normal contacts 21by the switch shaft when it reaches normalposition.

Control relay of the trunk busying switch I), upon deenergizing, inresponse to the opening of its circuit at armature of repeating relay 12of switch F, opens the circuit of release relay 76 at armature 86, andcloses the previously traced circuit for slow acting relay 78 and rotarymagnet 81. Rotary magnet 81, upon energizing, dvances the switch wiperinto engagement with the next contact. Relay energizes, but does nothave any particular function at this Relay 76, upon deenergizng, opensthe circuit of relay 78 and rotary magnet 81 at armature SS and closesthe circuit or" the release magnet 82 by way oi release link spring 85and its working; con tact. Release magnet 82, upon ems-gi ting, forcesthe double dog 83 out of engagement with the switch shalt, whereuponrelease link 84 drops over the end of the said double dog, therebyretaining it in place. Release link spring 85, upon moving downward atthis time opens the circuit of release magnet 82 and closes the circuitthe slow acting relay which is assumed to be associated with the ofinormal contact 93. The shaft and wiper the switch. D are new restored tonormal position in the usual manner, the circuit of the slowacting relayassociated with on" normal contact .93 being opened by the switch shaftat the said ofi" normal contact as soon as the said shaft reaches normalposition. The entire connection is now released and is ready for anysubsequent calls whichthe wire chiei may desire to make.

The various features of the invention,

having been thus described and ascertained,

Lil

iii)

will now be pointed out in the appended claims.

hat I claim as my invention is:

1. In a telephone system, a main exchange and a branch exchange, aplurality of two way two conductor trunk lines connecting saidexchanges, a wire chicfs testing trunk connecting said exchanges, a testswitch in the branch exchange for connecting said test trunk with anyone of said two way trunk lines, means for clearing the selected trunkfor testing at the branch exchange end thereof when the connection isestablished, and means operating automatically at the same time forclearing the selected trunk at the main exchange end thereof.

2. In a telephone system, a two way trunk line extending between distantexchanges, a normally'closed relay bridge across the trunk line at eachexchange, a test switch for use by a wire chiei in setting up a testingconnection with said trunk line, and means operated independent ofcontrol over the trunk line when the testing connection is establishedfor opening both relay bridges to permit the trunk line to be tested.

3. In a telephone system, a two way trunk line extending between distantexchanges, a normally closed relay bridge across the trunk line at eachexchange, wire chiefs testing equipment in the first exchange, meansincluding a test switch in the second exchange for setting up a testingconnection with said trunk line, an auxiliary switch in the firstexchange operated simultaneously with said test switch, and meanscontrolled by said switches for opening both relay bridges when thetesting connection is esta lished.

4. In a telephone system, a two way trunk line extending between twoexchanges and terminating at each exchange in an automatic switch, aline relay in each switch normally connected in bridge of said trunkline, another switch "for connecting with said trunk line in oneexchange, and means ef fective when the trunk line is connected with andwhile the associated switches are at normal for disconnecting both saidline relays to prevent the operation of the associated switches.

In a telephone system, a two way trunk ine extending between twoexchanges and erminating at each exchange in an automatic switch, a linerelay in each switch normally connected in bridge of said trunk line, athird switch for connecting with said trunk line in the first exchange,means for disconnecting the line relay in the first exchange when thetrunk line is connected with, a fourth switch in the .second exchange,operating simultaneously with said third switch, means controlled bysaid fourth switch for disconnecting the other line relay and means forcausing said third and :tourth switches to operate simultaneously setforth.

6. In a telephone system, a two way trunk line, a normally closed relaybridge across said trunk line at both ends, the relay at either endbeing normally responsive when the trunk line is taken for use at theother end in the process of setting up a talking connection, testingmeans for connecting with said trunk line at one end, and means foropening both bridges when the trunk line is connected With, by saidtesting means, while preventing the relays in said bridges fromoperating.

7. In a telephone system, a two way trunk line connecting two exchanges,a normally closed relay bridge across said trunk line at both ends, arelay in each bridge normally operated when the trunk line is connectedwith at the other exchange, means at each exchange for establishing suchconnections, additional means in one exchange for con necting with saidtrunk line, the relays in both bridges remaining inoperative, and meansfor opening both bridges when the trunk line is connected with.

8. In a telephone system. a two way trunk line extending between distantexchanges, automatic trunking switches in both exchanges having accessto said trunk line, a. wire chiets test switch in one exchange alsohaving access to said trunk line, and means operative independent ofcurrent flow over said trunk line whenever the said trunk line isconnected with by way of said test switch for rendering the trunk linebusy to the said trunking switches.

9. In a telephone system, a trunk line terminating in an automaticswitch, means for connecting with said trunk over one path,

means responsive to such connection for operating said switch. means forconnecting with said trunk line at the same end over another path afterthe first connection is released. and means actuated automaticallyduring the establishment of the second connection for preventing theoperation of said switch.

10. In a telephone system. a trunk line, two automatic switches.contacts in the banks of said switches assigned to the two ends ol saidtrunk line, respective y, and a single directively controlled illlDlL-Etransmitting device for operating said switches in synchronism to selectsaid emit-acts simultaneously.

11. In a. telephone system, a trunk line. two automatic switches,rontacts in the banks of said switches assigned to the two ends of saidtrunk line, respectively, a single device for operating said switches insynchronism to select said contacts simultaneously, a cutoff relay atone end of said trunk line controlled via one oii said contacts, and acut-off relay the other end of trunk line 'l on controlled over theother of said contacts.

12. In a telephone system, an automatic switch. a trunk line accessibleto said switch and terminating in a second switch, a second trunk lineaccessible to said second switch, means for operating said switchessuccessively to extend a connection to said' second trunk line, anauxiliary switch inactive while the first switch is being operated,meansin the first switch for operating the auxiliary switchsimultaneously with the second switch, and a contact in the bank of saidauxiliary switch assigned to said second trunk line.

13. In a testing system for trunk lines, a plurality of serially relatedswitches for selecting a trunk line at the remote end thereof, anauxiliary switch for selecting the same trunk line at the near endthereof, and means for operating said last switch in synchronism withthe final switch of-said plurality.

1.4. In a testing system for trunk lines, a plurality of seriallyrelated switches for selecting a trunk line at the remote end thereof,an auxiliary switch for selecting the same trunk line at the near endthereof, iii-cans for operating said last switch in synchronism with thefinal switch of said plu- 'ality, a testing circuit including saidplurality of switches, and means for clearing the trunk line for testingcontrolledby said auxiliary switch.

15. In a telephone system, two automatic switches in serial relation, anauxiliary switch individual to said first switch, a line relay foroperating said first switch to connect with said second switch, a secondline clay controlled by said first line relay. control circuits for saidsecond switch and said auxiliary switch controlled by said second linerela and means responsive to the completion of said connection forclosing said circuits.

16. In a. telephone testing system, groups of trunks, test connectorshaving access to said trunks over bank contacts individual to saidtrunks, ea h test connector having access to only a particular one ofsaid groups. a test distributor having access to all of said testconnectors, a trunk busying switch associated with said test distributorhaving access to bank contacts each of which is connnon to acorresponding guarding condnctor in each of said groups of trunks butnormally disconnected therefrom, means for operating said testdistributor to seize one of said. test connectors and to connect thecommon bank contacts to corresponding guarding conductors of the groupof trunks to which the seized connector has access, and means foroperating the seized test connector and said switch to seize and busyover said contacts any one of said trunks in the group to which the saidconnector has access. y

17. In a telephone testing system, groups of trunk lines, said trunksterminating at one end in bank contacts individual thereto, testconnectors having access to said bank contacts for testing purposes,said trunks having guarding conductors at the other end; bank contactscommon to all said guarding conductors but normally disconnectedtherefrom, an auxiliary switch having access to said common bankcontacts, means for connecting the guarding conductors of any one ofsaid groups of trunks to said bank contacts to the exclusion of theother groups of guarding conductors, and means for operating said testconnectors and said auxiliary switch to seize said trunks and to makethe seized trunks busy at both. ends.

18. In a telephone system, a main exchange, a plurality of branchexchanges, a group of trunk lines connecting each branch exchangewith'said main exchange, guarding conductors for all of said trunk linesat the main exchange, a trunk busying switch at the main exchange alevel of bank contacts in said switch, said level common to all of saidguarding conductors but normally disconnected therefrom, and meanswhereby the guarding conductors of any one of said groups of trunk linesmay be connected to said level of bank contacts to the exclusion of theother groups of guarding conductors.

19. In a telephone testing system, groups of trunks, a trunk busyingswitch, bank contacts accessible to said switch, the first of saidcontacts being common to the first of said trunks in each of said groupsbut normally disconnected therefrom, and means forconnecting said firstcontact with the first trunk in any one of said groups withoutconnecting the first contact to the first trunk in the remaining groups.

20. In a telephone testing system, groups of trunks, a trunk busyingswitch, bank contacts accessible to said switch, the first of saidcontacts being common to the first of said trunks in each of said groupsbut normally disconnected therefrom, means for connecting said firstcontact with the first trunk in any one of said groups withoutconnecting the first contact to the first trunk in the remaining groups,and means for operating said switch to connect with said first contactto busy whichever first trunk the contact may be connected to.

' 21. In a telephone testing system, groups of trunks, a trunk busyingswitch, bank contacts in said switch, each of said contacts being commonto a corresponding trunk in each of said groups but normallydisconnected therefrom, and means for connecting said contacts withcorresponding trunks of any one of said groups Without connecting saidcontacts to corresponding trunks of the remaining groups.

22. In a telephone testing system, roups of trunks, a trunk busyingswitch, bank contacts in said switch, each of said contacts being commonto a corresponding trunk in each of said groups but normallydisconnected therefrom, means for connecting said contacts Withcorresponding trunks of any one of said groups without connecting saidcontacts to corresponding trunks of the remaining groups and means foroperating said switch to connect With any one of said contacts to busyWhichever trunk the said one contact is connected with.

In Witness whereof, I hereunto subscribe my name this 29th day ofAugust, A. 1).,

CLARENCE ERNEST LOMAX.

